Flash media has advantages over RAM and hard disk storage, namely that unlike RAM, flash media is persistent, and unlike hard disk storage, flash media provides much faster data access times, e.g., on the order of hundreds or thousands of times faster than hard disk access. Many applications thus may benefit from the use of flash media.
However, flash media is expensive, at present costing ten to twenty times more per gigabyte than hard disk storage. Further, flash devices are subject to reduced lifetimes due to page wearing, whereby small random writes (that also have relatively high latency) are not desirable. What is desirable is a technology for using flash media (or other non-RAM, non-hard disk storage) that provides high performance, while factoring in cost considerations, efficiency and media lifetimes.
U.S. patent application Ser. No. 12/773,859, assigned to the assignee of the present invention and herein incorporated by reference, describes a flash-based or other secondary storage memory cache having these desired characteristics, such as for use in storing key-value pairs. However, the amount of RAM used is on the order of six bytes (two signature bytes plus four pointer bytes) for each key-value pair maintained in secondary (e.g., flash) storage. Reducing the amount of RAM used is desirable in many scenarios.